The invention relates to a safety system for a motor vehicle having an internal-combustion engine.
German Patent Document 39 14 167 A1 discloses a safety system for a motor vehicle internal-combustion engine in which the output torque of a transmission is monitored. If the determined torque exceeds a given minimal value, when the accelerator pedal is not depressed, operation of the internal-combustion engine is interrupted. This system has the disadvantage that it engages only when the accelerator pedal is not depressed. It cannot recognize other faulty functions.
In addition, systems are known which the throttle valve position is monitored. These systems have the disadvantage that a single quantity is used both for controlling the internal-combustion engine and for monitoring. Should a fault occur in this sensing, both the engine control and the monitoring device will operate with the wrong quantity. Another problem of this monitoring device occurs in the case of internal-combustion engines with a dynamic torque adjustment in which, particularly in dynamic operating conditions, there is no direct relationship between the throttle valve position and the engine load. Thus, in the case of such internal-combustion engines, monitoring cannot occur on the basis of the throttle valve position.
It is an object of the present invention to provide a safety system for a motor vehicle with an internal-combustion engine which ensures the safety of the motor vehicle in all operating ranges, and which can also be used for internal-combustion engines with a dynamic torque adjustment.
These and other objects and advantages are achieved according to the invention by using distinct independent quantities for controlling the engine on the one hand and for monitoring engine control on the other. According to the invention, control of the internal-combustion engine may be performed, for example, by way of an operating parameter indicative of engine load. Preferably, monitoring of the engine control is integrated into a traction control system, in which case the desired value for a quantity indicative of vehicle propulsion, such as the output torque, is transmitted by the engine control to the monitoring system, while the actual output torque is determined in the traction control system from the rotational wheel speed. If a fault is recognized in the traction control system during the continuous comparison of desired values and actual values, a signal is transmitted back to the engine control unit for influencing the engine control.
The safety system according to the invention has the advantage that, because independent quantities are used for the engine control and for the monitoring, if the sensing of one of the two quantities or one of the two control units fails, the other control unit can continue to operate properly, and to ensure at least an emergency operation or render the internal-combustion engine inoperative.
When the safety system is used in a vehicle having a traction control system, it can be integrated in the traction control system. This has the advantage that the rotational wheel speed is detected and processed directly by the traction control system. In addition, the traction control system has a high-priority access to the torque indication in the engine control. Existing connections can therefore be used for the communication between the safety system and the engine control.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.